This invention relates to gas-insulated switchgears and more particularly to gas-insulated disconnectors provided with structures for suppressing the contamination of the insulating gas with the metal particles generated by the abrasion of the surfaces of contacts in sliding contact.
FIG. 6 is a sectional view of a conventional gas-insulated disconnector, which is disclosed, for example, in Mitsubishi Denki Gihou (Technical Journal of Mitsubishi Electric), Vol. 53, No. 10, p. 770, FIG. 5, Vol. 54, No. 6, p. 22, FIG. 6, and Vol. 51, No. 6, p. 380, FIG. 7.
To a movable contact 1 is coupled an operating rod 2. A tulip-type sliding contact 3 includes a helical spring 3a which bundles the contact plates 3b together and urges them upon the movable contact 1 and the top end portion of the support member 4, such that the sliding contact 3 ensures electrical connection between the sliding contact 3 and the support member 4. A Scott-Russel type link mechanism 5 converts the rotational motion around the rotational axis 6, which is disposed perpendicular to the sheet of the drawing, into the linear vertical motion of the operating rod 2. An operation device (not shown) is coupled to the rotational axis 6 through an electrically insulating rotation rod (not shown). A shield 7 surrounding the movable contact 1 and the support member 4 mollifies the electric field. When the movable contact 1 slides into a tulip-shaped fixed contact 10, a ring-shaped helical spring 10a urges the fixed contact 10 upon the movable contact 1, and the fixed contact 10 electrically couples the movable contact 1 and the support member 11. A shield 12 surrounding the fixed contact 10 mollifies the electric field.
Upper and lower insulating spacers 8, hermetically sealing upper and lower openings, respectively, of a housing 9 filled with an electrically insulating gas such as SF6, support central conductors 8a at the center thereof which are secured to the support member 4 and the support member 11, respectively. Sliding contacts 13 urged inwards by the helical springs 13a electrically connect the central conductors 8a to electrical conductors 14 and 15, respectively, of neighboring electrical apparatus. Shields 16 surrounding the respective sliding contacts 13 mollifies the electric field thereat.
In FIG. 6 the disconnector is shown in an open state. The making of the disconnector from the state shown in FIG. 6 proceeds as follows. Through the insulating rod, the operation device rotates the rotational axis 6 clockwise in the direction of the arrow A. The rotation of the rotational axis 6 is converted by means of the link mechanism 5 into an upward linear motion of the operating rod 2. Thus, the operating rod 2 moves upward together with the movable contact 1 until the head of the movable contact 1 is received into the fixed contact 10. The helical spring 10a urges the fixed contact 10 upon the movable contact 1 sliding thereinto, and the circuit between the upper conductor 14 and the lower conductor 15 is closed through: the upper sliding contact 13, the upper central conductor 8a, the support member 11, the fixed contact 10, the movable contact 1, the sliding contact 3, the support member 4, the lower central conductor 8a, and the lower sliding contact 13.
On the other hand, the breaking operation from the closed state is performed as follows. By means of the insulating rod and the operation device (not shown), the rotational axis 6 is rotated counter-clockwise in the direction opposite to the arrow A. The rotation is converted by means of the link mechanism 5 into a downward linear motion of the operating rod 2. Thus, the movable contact 1 moves downward with the operating rod 2 and leaves the fixed contact 10. Finally the movable contact 1 reaches the position shown in FIG. 6.
The conventional gas-insulated disconnector, however, has the following disadvantage. When the disconnector is made or opened, the operating rod 2 slides upon the fixed contact 10, the sliding contact 3 and the support member 4. The abrasion caused by the sliding movement between these metallic members generates small metal particles, which may drift into the insulating gas such as SF.sub.6 filling the housing 9 to ensure insulation between the contacts 1 and 10, etc. The insulation efficiency is reduced by the contamination of the insulating gas with the metal particles. The deterioration of the insulation efficiency is all the more serious since the contacts are usually plated with silver to improve the conducting efficiency while the soft silver platings are easily abraded to produce contaminating small metal particles.